[PATCH 1/1] FS/JBD:replace count*size kmalloc by kmalloc_array

[PATCH 1/1] FS/JBD:replace count*size kmalloc by kmalloc_array

[Fabian Frederick]

kmalloc_array manages count*sizeof overflow.

This patch also fixes checkpatch warnings:
ERROR: "(foo*)" should be "(foo *)"

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
 fs/jbd/journal.c | 6 ++++--
 fs/jbd/revoke.c  | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 06fe11e..26ebba7 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -810,7 +810,8 @@ journal_t * journal_init_dev(struct block_device *bdev,
 	journal->j_blocksize = blocksize;
 	n = journal->j_blocksize / sizeof(journal_block_tag_t);
 	journal->j_wbufsize = n;
-	journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
+	journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
+					GFP_KERNEL);
 	if (!journal->j_wbuf) {
 		printk(KERN_ERR "%s: Can't allocate bhs for commit thread\n",
 			__func__);
@@ -871,7 +872,8 @@ journal_t * journal_init_inode (struct inode *inode)
 	/* journal descriptor can store up to n blocks -bzzz */
 	n = journal->j_blocksize / sizeof(journal_block_tag_t);
 	journal->j_wbufsize = n;
-	journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
+	journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
+					GFP_KERNEL);
 	if (!journal->j_wbuf) {
 		printk(KERN_ERR "%s: Can't allocate bhs for commit thread\n",
 			__func__);
diff --git a/fs/jbd/revoke.c b/fs/jbd/revoke.c
index 8898bbd..7374a57 100644
--- a/fs/jbd/revoke.c
+++ b/fs/jbd/revoke.c
@@ -241,7 +241,7 @@ static struct jbd_revoke_table_s *journal_init_revoke_table(int hash_size)
 	table->hash_size = hash_size;
 	table->hash_shift = ilog2(hash_size);
 	table->hash_table =
-		kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
+		kmalloc_array(hash_size, sizeof(struct list_head), GFP_KERNEL);
 	if (!table->hash_table) {
 		kmem_cache_free(revoke_table_cache, table);
 		table = NULL;
-- 
1.9.1

Re: [PATCH 1/1] FS/JBD:replace count*size kmalloc by kmalloc_array

[Theodore Ts'o]

On Wed, Jun 25, 2014 at 08:49:06PM +0200, Fabian Frederick wrote:
> kmalloc_array manages count*sizeof overflow.

Except in these call sites, overflow is impossible.

kmalloc_array() is useful when count is coming from an unvalidated
source.  But in this case, the count is either a fixed, hard-coded
value (256), or the size of n*count is *guaranteed* to be less than
the page size.

So this just adds some extra code which is pointless (assuming the
compiler isn't smart enough to optimize it out).

	       	     	       		   - Ted